blob: 6eb837ed0fed8d20f1395a6c7777cc9e7eb77210 [file] [log] [blame]
use crate::cmp;
use crate::fmt;
use crate::intrinsics;
use crate::ops::{Add, AddAssign, Try};
use crate::usize;
use super::{from_fn, LoopState};
use super::{DoubleEndedIterator, ExactSizeIterator, FusedIterator, Iterator, TrustedLen};
mod chain;
mod flatten;
mod zip;
pub use self::chain::Chain;
#[stable(feature = "rust1", since = "1.0.0")]
pub use self::flatten::{FlatMap, Flatten};
pub(crate) use self::zip::TrustedRandomAccess;
pub use self::zip::Zip;
/// A double-ended iterator with the direction inverted.
///
/// This `struct` is created by the [`rev`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`rev`]: trait.Iterator.html#method.rev
/// [`Iterator`]: trait.Iterator.html
#[derive(Clone, Debug)]
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Rev<T> {
iter: T,
}
impl<T> Rev<T> {
pub(super) fn new(iter: T) -> Rev<T> {
Rev { iter }
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> Iterator for Rev<I>
where
I: DoubleEndedIterator,
{
type Item = <I as Iterator>::Item;
#[inline]
fn next(&mut self) -> Option<<I as Iterator>::Item> {
self.iter.next_back()
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
#[inline]
fn nth(&mut self, n: usize) -> Option<<I as Iterator>::Item> {
self.iter.nth_back(n)
}
fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R
where
Self: Sized,
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,
{
self.iter.try_rfold(init, f)
}
fn fold<Acc, F>(self, init: Acc, f: F) -> Acc
where
F: FnMut(Acc, Self::Item) -> Acc,
{
self.iter.rfold(init, f)
}
#[inline]
fn find<P>(&mut self, predicate: P) -> Option<Self::Item>
where
P: FnMut(&Self::Item) -> bool,
{
self.iter.rfind(predicate)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> DoubleEndedIterator for Rev<I>
where
I: DoubleEndedIterator,
{
#[inline]
fn next_back(&mut self) -> Option<<I as Iterator>::Item> {
self.iter.next()
}
#[inline]
fn nth_back(&mut self, n: usize) -> Option<<I as Iterator>::Item> {
self.iter.nth(n)
}
fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R
where
Self: Sized,
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,
{
self.iter.try_fold(init, f)
}
fn rfold<Acc, F>(self, init: Acc, f: F) -> Acc
where
F: FnMut(Acc, Self::Item) -> Acc,
{
self.iter.fold(init, f)
}
fn rfind<P>(&mut self, predicate: P) -> Option<Self::Item>
where
P: FnMut(&Self::Item) -> bool,
{
self.iter.find(predicate)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> ExactSizeIterator for Rev<I>
where
I: ExactSizeIterator + DoubleEndedIterator,
{
fn len(&self) -> usize {
self.iter.len()
}
fn is_empty(&self) -> bool {
self.iter.is_empty()
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<I> FusedIterator for Rev<I> where I: FusedIterator + DoubleEndedIterator {}
#[unstable(feature = "trusted_len", issue = "37572")]
unsafe impl<I> TrustedLen for Rev<I> where I: TrustedLen + DoubleEndedIterator {}
/// An iterator that copies the elements of an underlying iterator.
///
/// This `struct` is created by the [`copied`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`copied`]: trait.Iterator.html#method.copied
/// [`Iterator`]: trait.Iterator.html
#[stable(feature = "iter_copied", since = "1.36.0")]
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[derive(Clone, Debug)]
pub struct Copied<I> {
it: I,
}
impl<I> Copied<I> {
pub(super) fn new(it: I) -> Copied<I> {
Copied { it }
}
}
fn copy_fold<T: Copy, Acc>(mut f: impl FnMut(Acc, T) -> Acc) -> impl FnMut(Acc, &T) -> Acc {
move |acc, &elt| f(acc, elt)
}
fn copy_try_fold<T: Copy, Acc, R>(mut f: impl FnMut(Acc, T) -> R) -> impl FnMut(Acc, &T) -> R {
move |acc, &elt| f(acc, elt)
}
#[stable(feature = "iter_copied", since = "1.36.0")]
impl<'a, I, T: 'a> Iterator for Copied<I>
where
I: Iterator<Item = &'a T>,
T: Copy,
{
type Item = T;
fn next(&mut self) -> Option<T> {
self.it.next().copied()
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.it.size_hint()
}
fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R
where
Self: Sized,
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,
{
self.it.try_fold(init, copy_try_fold(f))
}
fn fold<Acc, F>(self, init: Acc, f: F) -> Acc
where
F: FnMut(Acc, Self::Item) -> Acc,
{
self.it.fold(init, copy_fold(f))
}
}
#[stable(feature = "iter_copied", since = "1.36.0")]
impl<'a, I, T: 'a> DoubleEndedIterator for Copied<I>
where
I: DoubleEndedIterator<Item = &'a T>,
T: Copy,
{
fn next_back(&mut self) -> Option<T> {
self.it.next_back().copied()
}
fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R
where
Self: Sized,
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,
{
self.it.try_rfold(init, copy_try_fold(f))
}
fn rfold<Acc, F>(self, init: Acc, f: F) -> Acc
where
F: FnMut(Acc, Self::Item) -> Acc,
{
self.it.rfold(init, copy_fold(f))
}
}
#[stable(feature = "iter_copied", since = "1.36.0")]
impl<'a, I, T: 'a> ExactSizeIterator for Copied<I>
where
I: ExactSizeIterator<Item = &'a T>,
T: Copy,
{
fn len(&self) -> usize {
self.it.len()
}
fn is_empty(&self) -> bool {
self.it.is_empty()
}
}
#[stable(feature = "iter_copied", since = "1.36.0")]
impl<'a, I, T: 'a> FusedIterator for Copied<I>
where
I: FusedIterator<Item = &'a T>,
T: Copy,
{
}
#[doc(hidden)]
unsafe impl<'a, I, T: 'a> TrustedRandomAccess for Copied<I>
where
I: TrustedRandomAccess<Item = &'a T>,
T: Copy,
{
unsafe fn get_unchecked(&mut self, i: usize) -> Self::Item {
*self.it.get_unchecked(i)
}
#[inline]
fn may_have_side_effect() -> bool {
I::may_have_side_effect()
}
}
#[stable(feature = "iter_copied", since = "1.36.0")]
unsafe impl<'a, I, T: 'a> TrustedLen for Copied<I>
where
I: TrustedLen<Item = &'a T>,
T: Copy,
{
}
/// An iterator that clones the elements of an underlying iterator.
///
/// This `struct` is created by the [`cloned`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`cloned`]: trait.Iterator.html#method.cloned
/// [`Iterator`]: trait.Iterator.html
#[stable(feature = "iter_cloned", since = "1.1.0")]
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[derive(Clone, Debug)]
pub struct Cloned<I> {
it: I,
}
impl<I> Cloned<I> {
pub(super) fn new(it: I) -> Cloned<I> {
Cloned { it }
}
}
fn clone_try_fold<T: Clone, Acc, R>(mut f: impl FnMut(Acc, T) -> R) -> impl FnMut(Acc, &T) -> R {
move |acc, elt| f(acc, elt.clone())
}
#[stable(feature = "iter_cloned", since = "1.1.0")]
impl<'a, I, T: 'a> Iterator for Cloned<I>
where
I: Iterator<Item = &'a T>,
T: Clone,
{
type Item = T;
fn next(&mut self) -> Option<T> {
self.it.next().cloned()
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.it.size_hint()
}
fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R
where
Self: Sized,
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,
{
self.it.try_fold(init, clone_try_fold(f))
}
fn fold<Acc, F>(self, init: Acc, f: F) -> Acc
where
F: FnMut(Acc, Self::Item) -> Acc,
{
self.it.map(T::clone).fold(init, f)
}
}
#[stable(feature = "iter_cloned", since = "1.1.0")]
impl<'a, I, T: 'a> DoubleEndedIterator for Cloned<I>
where
I: DoubleEndedIterator<Item = &'a T>,
T: Clone,
{
fn next_back(&mut self) -> Option<T> {
self.it.next_back().cloned()
}
fn try_rfold<B, F, R>(&mut self, init: B, f: F) -> R
where
Self: Sized,
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,
{
self.it.try_rfold(init, clone_try_fold(f))
}
fn rfold<Acc, F>(self, init: Acc, f: F) -> Acc
where
F: FnMut(Acc, Self::Item) -> Acc,
{
self.it.map(T::clone).rfold(init, f)
}
}
#[stable(feature = "iter_cloned", since = "1.1.0")]
impl<'a, I, T: 'a> ExactSizeIterator for Cloned<I>
where
I: ExactSizeIterator<Item = &'a T>,
T: Clone,
{
fn len(&self) -> usize {
self.it.len()
}
fn is_empty(&self) -> bool {
self.it.is_empty()
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<'a, I, T: 'a> FusedIterator for Cloned<I>
where
I: FusedIterator<Item = &'a T>,
T: Clone,
{
}
#[doc(hidden)]
unsafe impl<'a, I, T: 'a> TrustedRandomAccess for Cloned<I>
where
I: TrustedRandomAccess<Item = &'a T>,
T: Clone,
{
default unsafe fn get_unchecked(&mut self, i: usize) -> Self::Item {
self.it.get_unchecked(i).clone()
}
#[inline]
default fn may_have_side_effect() -> bool {
true
}
}
#[doc(hidden)]
unsafe impl<'a, I, T: 'a> TrustedRandomAccess for Cloned<I>
where
I: TrustedRandomAccess<Item = &'a T>,
T: Copy,
{
unsafe fn get_unchecked(&mut self, i: usize) -> Self::Item {
*self.it.get_unchecked(i)
}
#[inline]
fn may_have_side_effect() -> bool {
I::may_have_side_effect()
}
}
#[unstable(feature = "trusted_len", issue = "37572")]
unsafe impl<'a, I, T: 'a> TrustedLen for Cloned<I>
where
I: TrustedLen<Item = &'a T>,
T: Clone,
{
}
/// An iterator that repeats endlessly.
///
/// This `struct` is created by the [`cycle`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`cycle`]: trait.Iterator.html#method.cycle
/// [`Iterator`]: trait.Iterator.html
#[derive(Clone, Debug)]
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Cycle<I> {
orig: I,
iter: I,
}
impl<I: Clone> Cycle<I> {
pub(super) fn new(iter: I) -> Cycle<I> {
Cycle { orig: iter.clone(), iter }
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> Iterator for Cycle<I>
where
I: Clone + Iterator,
{
type Item = <I as Iterator>::Item;
#[inline]
fn next(&mut self) -> Option<<I as Iterator>::Item> {
match self.iter.next() {
None => {
self.iter = self.orig.clone();
self.iter.next()
}
y => y,
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
// the cycle iterator is either empty or infinite
match self.orig.size_hint() {
sz @ (0, Some(0)) => sz,
(0, _) => (0, None),
_ => (usize::MAX, None),
}
}
#[inline]
fn try_fold<Acc, F, R>(&mut self, mut acc: Acc, mut f: F) -> R
where
F: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
// fully iterate the current iterator. this is necessary because
// `self.iter` may be empty even when `self.orig` isn't
acc = self.iter.try_fold(acc, &mut f)?;
self.iter = self.orig.clone();
// complete a full cycle, keeping track of whether the cycled
// iterator is empty or not. we need to return early in case
// of an empty iterator to prevent an infinite loop
let mut is_empty = true;
acc = self.iter.try_fold(acc, |acc, x| {
is_empty = false;
f(acc, x)
})?;
if is_empty {
return Try::from_ok(acc);
}
loop {
self.iter = self.orig.clone();
acc = self.iter.try_fold(acc, &mut f)?;
}
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<I> FusedIterator for Cycle<I> where I: Clone + Iterator {}
/// An iterator for stepping iterators by a custom amount.
///
/// This `struct` is created by the [`step_by`] method on [`Iterator`]. See
/// its documentation for more.
///
/// [`step_by`]: trait.Iterator.html#method.step_by
/// [`Iterator`]: trait.Iterator.html
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "iterator_step_by", since = "1.28.0")]
#[derive(Clone, Debug)]
pub struct StepBy<I> {
iter: I,
step: usize,
first_take: bool,
}
impl<I> StepBy<I> {
pub(super) fn new(iter: I, step: usize) -> StepBy<I> {
assert!(step != 0);
StepBy { iter, step: step - 1, first_take: true }
}
}
#[stable(feature = "iterator_step_by", since = "1.28.0")]
impl<I> Iterator for StepBy<I>
where
I: Iterator,
{
type Item = I::Item;
#[inline]
fn next(&mut self) -> Option<Self::Item> {
if self.first_take {
self.first_take = false;
self.iter.next()
} else {
self.iter.nth(self.step)
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
#[inline]
fn first_size(step: usize) -> impl Fn(usize) -> usize {
move |n| if n == 0 { 0 } else { 1 + (n - 1) / (step + 1) }
}
#[inline]
fn other_size(step: usize) -> impl Fn(usize) -> usize {
move |n| n / (step + 1)
}
let (low, high) = self.iter.size_hint();
if self.first_take {
let f = first_size(self.step);
(f(low), high.map(f))
} else {
let f = other_size(self.step);
(f(low), high.map(f))
}
}
#[inline]
fn nth(&mut self, mut n: usize) -> Option<Self::Item> {
if self.first_take {
self.first_take = false;
let first = self.iter.next();
if n == 0 {
return first;
}
n -= 1;
}
// n and self.step are indices, we need to add 1 to get the amount of elements
// When calling `.nth`, we need to subtract 1 again to convert back to an index
// step + 1 can't overflow because `.step_by` sets `self.step` to `step - 1`
let mut step = self.step + 1;
// n + 1 could overflow
// thus, if n is usize::MAX, instead of adding one, we call .nth(step)
if n == usize::MAX {
self.iter.nth(step - 1);
} else {
n += 1;
}
// overflow handling
loop {
let mul = n.checked_mul(step);
{
if intrinsics::likely(mul.is_some()) {
return self.iter.nth(mul.unwrap() - 1);
}
}
let div_n = usize::MAX / n;
let div_step = usize::MAX / step;
let nth_n = div_n * n;
let nth_step = div_step * step;
let nth = if nth_n > nth_step {
step -= div_n;
nth_n
} else {
n -= div_step;
nth_step
};
self.iter.nth(nth - 1);
}
}
fn try_fold<Acc, F, R>(&mut self, mut acc: Acc, mut f: F) -> R
where
F: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
#[inline]
fn nth<I: Iterator>(iter: &mut I, step: usize) -> impl FnMut() -> Option<I::Item> + '_ {
move || iter.nth(step)
}
if self.first_take {
self.first_take = false;
match self.iter.next() {
None => return Try::from_ok(acc),
Some(x) => acc = f(acc, x)?,
}
}
from_fn(nth(&mut self.iter, self.step)).try_fold(acc, f)
}
}
impl<I> StepBy<I>
where
I: ExactSizeIterator,
{
// The zero-based index starting from the end of the iterator of the
// last element. Used in the `DoubleEndedIterator` implementation.
fn next_back_index(&self) -> usize {
let rem = self.iter.len() % (self.step + 1);
if self.first_take {
if rem == 0 { self.step } else { rem - 1 }
} else {
rem
}
}
}
#[stable(feature = "double_ended_step_by_iterator", since = "1.38.0")]
impl<I> DoubleEndedIterator for StepBy<I>
where
I: DoubleEndedIterator + ExactSizeIterator,
{
#[inline]
fn next_back(&mut self) -> Option<Self::Item> {
self.iter.nth_back(self.next_back_index())
}
#[inline]
fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
// `self.iter.nth_back(usize::MAX)` does the right thing here when `n`
// is out of bounds because the length of `self.iter` does not exceed
// `usize::MAX` (because `I: ExactSizeIterator`) and `nth_back` is
// zero-indexed
let n = n.saturating_mul(self.step + 1).saturating_add(self.next_back_index());
self.iter.nth_back(n)
}
fn try_rfold<Acc, F, R>(&mut self, init: Acc, mut f: F) -> R
where
F: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
#[inline]
fn nth_back<I: DoubleEndedIterator>(
iter: &mut I,
step: usize,
) -> impl FnMut() -> Option<I::Item> + '_ {
move || iter.nth_back(step)
}
match self.next_back() {
None => Try::from_ok(init),
Some(x) => {
let acc = f(init, x)?;
from_fn(nth_back(&mut self.iter, self.step)).try_fold(acc, f)
}
}
}
}
// StepBy can only make the iterator shorter, so the len will still fit.
#[stable(feature = "iterator_step_by", since = "1.28.0")]
impl<I> ExactSizeIterator for StepBy<I> where I: ExactSizeIterator {}
/// An iterator that maps the values of `iter` with `f`.
///
/// This `struct` is created by the [`map`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`map`]: trait.Iterator.html#method.map
/// [`Iterator`]: trait.Iterator.html
///
/// # Notes about side effects
///
/// The [`map`] iterator implements [`DoubleEndedIterator`], meaning that
/// you can also [`map`] backwards:
///
/// ```rust
/// let v: Vec<i32> = vec![1, 2, 3].into_iter().map(|x| x + 1).rev().collect();
///
/// assert_eq!(v, [4, 3, 2]);
/// ```
///
/// [`DoubleEndedIterator`]: trait.DoubleEndedIterator.html
///
/// But if your closure has state, iterating backwards may act in a way you do
/// not expect. Let's go through an example. First, in the forward direction:
///
/// ```rust
/// let mut c = 0;
///
/// for pair in vec!['a', 'b', 'c'].into_iter()
/// .map(|letter| { c += 1; (letter, c) }) {
/// println!("{:?}", pair);
/// }
/// ```
///
/// This will print "('a', 1), ('b', 2), ('c', 3)".
///
/// Now consider this twist where we add a call to `rev`. This version will
/// print `('c', 1), ('b', 2), ('a', 3)`. Note that the letters are reversed,
/// but the values of the counter still go in order. This is because `map()` is
/// still being called lazily on each item, but we are popping items off the
/// back of the vector now, instead of shifting them from the front.
///
/// ```rust
/// let mut c = 0;
///
/// for pair in vec!['a', 'b', 'c'].into_iter()
/// .map(|letter| { c += 1; (letter, c) })
/// .rev() {
/// println!("{:?}", pair);
/// }
/// ```
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct Map<I, F> {
iter: I,
f: F,
}
impl<I, F> Map<I, F> {
pub(super) fn new(iter: I, f: F) -> Map<I, F> {
Map { iter, f }
}
}
#[stable(feature = "core_impl_debug", since = "1.9.0")]
impl<I: fmt::Debug, F> fmt::Debug for Map<I, F> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Map").field("iter", &self.iter).finish()
}
}
fn map_fold<T, B, Acc>(
mut f: impl FnMut(T) -> B,
mut g: impl FnMut(Acc, B) -> Acc,
) -> impl FnMut(Acc, T) -> Acc {
move |acc, elt| g(acc, f(elt))
}
fn map_try_fold<'a, T, B, Acc, R>(
f: &'a mut impl FnMut(T) -> B,
mut g: impl FnMut(Acc, B) -> R + 'a,
) -> impl FnMut(Acc, T) -> R + 'a {
move |acc, elt| g(acc, f(elt))
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: Iterator, F> Iterator for Map<I, F>
where
F: FnMut(I::Item) -> B,
{
type Item = B;
#[inline]
fn next(&mut self) -> Option<B> {
self.iter.next().map(&mut self.f)
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
fn try_fold<Acc, G, R>(&mut self, init: Acc, g: G) -> R
where
Self: Sized,
G: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
self.iter.try_fold(init, map_try_fold(&mut self.f, g))
}
fn fold<Acc, G>(self, init: Acc, g: G) -> Acc
where
G: FnMut(Acc, Self::Item) -> Acc,
{
self.iter.fold(init, map_fold(self.f, g))
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for Map<I, F>
where
F: FnMut(I::Item) -> B,
{
#[inline]
fn next_back(&mut self) -> Option<B> {
self.iter.next_back().map(&mut self.f)
}
fn try_rfold<Acc, G, R>(&mut self, init: Acc, g: G) -> R
where
Self: Sized,
G: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
self.iter.try_rfold(init, map_try_fold(&mut self.f, g))
}
fn rfold<Acc, G>(self, init: Acc, g: G) -> Acc
where
G: FnMut(Acc, Self::Item) -> Acc,
{
self.iter.rfold(init, map_fold(self.f, g))
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: ExactSizeIterator, F> ExactSizeIterator for Map<I, F>
where
F: FnMut(I::Item) -> B,
{
fn len(&self) -> usize {
self.iter.len()
}
fn is_empty(&self) -> bool {
self.iter.is_empty()
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<B, I: FusedIterator, F> FusedIterator for Map<I, F> where F: FnMut(I::Item) -> B {}
#[unstable(feature = "trusted_len", issue = "37572")]
unsafe impl<B, I, F> TrustedLen for Map<I, F>
where
I: TrustedLen,
F: FnMut(I::Item) -> B,
{
}
#[doc(hidden)]
unsafe impl<B, I, F> TrustedRandomAccess for Map<I, F>
where
I: TrustedRandomAccess,
F: FnMut(I::Item) -> B,
{
unsafe fn get_unchecked(&mut self, i: usize) -> Self::Item {
(self.f)(self.iter.get_unchecked(i))
}
#[inline]
fn may_have_side_effect() -> bool {
true
}
}
/// An iterator that filters the elements of `iter` with `predicate`.
///
/// This `struct` is created by the [`filter`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`filter`]: trait.Iterator.html#method.filter
/// [`Iterator`]: trait.Iterator.html
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct Filter<I, P> {
iter: I,
predicate: P,
}
impl<I, P> Filter<I, P> {
pub(super) fn new(iter: I, predicate: P) -> Filter<I, P> {
Filter { iter, predicate }
}
}
#[stable(feature = "core_impl_debug", since = "1.9.0")]
impl<I: fmt::Debug, P> fmt::Debug for Filter<I, P> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Filter").field("iter", &self.iter).finish()
}
}
fn filter_fold<T, Acc>(
mut predicate: impl FnMut(&T) -> bool,
mut fold: impl FnMut(Acc, T) -> Acc,
) -> impl FnMut(Acc, T) -> Acc {
move |acc, item| if predicate(&item) { fold(acc, item) } else { acc }
}
fn filter_try_fold<'a, T, Acc, R: Try<Ok = Acc>>(
predicate: &'a mut impl FnMut(&T) -> bool,
mut fold: impl FnMut(Acc, T) -> R + 'a,
) -> impl FnMut(Acc, T) -> R + 'a {
move |acc, item| if predicate(&item) { fold(acc, item) } else { R::from_ok(acc) }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator, P> Iterator for Filter<I, P>
where
P: FnMut(&I::Item) -> bool,
{
type Item = I::Item;
#[inline]
fn next(&mut self) -> Option<I::Item> {
self.iter.find(&mut self.predicate)
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (_, upper) = self.iter.size_hint();
(0, upper) // can't know a lower bound, due to the predicate
}
// this special case allows the compiler to make `.filter(_).count()`
// branchless. Barring perfect branch prediction (which is unattainable in
// the general case), this will be much faster in >90% of cases (containing
// virtually all real workloads) and only a tiny bit slower in the rest.
//
// Having this specialization thus allows us to write `.filter(p).count()`
// where we would otherwise write `.map(|x| p(x) as usize).sum()`, which is
// less readable and also less backwards-compatible to Rust before 1.10.
//
// Using the branchless version will also simplify the LLVM byte code, thus
// leaving more budget for LLVM optimizations.
#[inline]
fn count(self) -> usize {
#[inline]
fn to_usize<T>(mut predicate: impl FnMut(&T) -> bool) -> impl FnMut(T) -> usize {
move |x| predicate(&x) as usize
}
self.iter.map(to_usize(self.predicate)).sum()
}
#[inline]
fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
self.iter.try_fold(init, filter_try_fold(&mut self.predicate, fold))
}
#[inline]
fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc
where
Fold: FnMut(Acc, Self::Item) -> Acc,
{
self.iter.fold(init, filter_fold(self.predicate, fold))
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: DoubleEndedIterator, P> DoubleEndedIterator for Filter<I, P>
where
P: FnMut(&I::Item) -> bool,
{
#[inline]
fn next_back(&mut self) -> Option<I::Item> {
self.iter.rfind(&mut self.predicate)
}
#[inline]
fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
self.iter.try_rfold(init, filter_try_fold(&mut self.predicate, fold))
}
#[inline]
fn rfold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc
where
Fold: FnMut(Acc, Self::Item) -> Acc,
{
self.iter.rfold(init, filter_fold(self.predicate, fold))
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<I: FusedIterator, P> FusedIterator for Filter<I, P> where P: FnMut(&I::Item) -> bool {}
/// An iterator that uses `f` to both filter and map elements from `iter`.
///
/// This `struct` is created by the [`filter_map`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`filter_map`]: trait.Iterator.html#method.filter_map
/// [`Iterator`]: trait.Iterator.html
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct FilterMap<I, F> {
iter: I,
f: F,
}
impl<I, F> FilterMap<I, F> {
pub(super) fn new(iter: I, f: F) -> FilterMap<I, F> {
FilterMap { iter, f }
}
}
#[stable(feature = "core_impl_debug", since = "1.9.0")]
impl<I: fmt::Debug, F> fmt::Debug for FilterMap<I, F> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("FilterMap").field("iter", &self.iter).finish()
}
}
fn filter_map_fold<T, B, Acc>(
mut f: impl FnMut(T) -> Option<B>,
mut fold: impl FnMut(Acc, B) -> Acc,
) -> impl FnMut(Acc, T) -> Acc {
move |acc, item| match f(item) {
Some(x) => fold(acc, x),
None => acc,
}
}
fn filter_map_try_fold<'a, T, B, Acc, R: Try<Ok = Acc>>(
f: &'a mut impl FnMut(T) -> Option<B>,
mut fold: impl FnMut(Acc, B) -> R + 'a,
) -> impl FnMut(Acc, T) -> R + 'a {
move |acc, item| match f(item) {
Some(x) => fold(acc, x),
None => R::from_ok(acc),
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: Iterator, F> Iterator for FilterMap<I, F>
where
F: FnMut(I::Item) -> Option<B>,
{
type Item = B;
#[inline]
fn next(&mut self) -> Option<B> {
self.iter.find_map(&mut self.f)
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (_, upper) = self.iter.size_hint();
(0, upper) // can't know a lower bound, due to the predicate
}
#[inline]
fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
self.iter.try_fold(init, filter_map_try_fold(&mut self.f, fold))
}
#[inline]
fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc
where
Fold: FnMut(Acc, Self::Item) -> Acc,
{
self.iter.fold(init, filter_map_fold(self.f, fold))
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I: DoubleEndedIterator, F> DoubleEndedIterator for FilterMap<I, F>
where
F: FnMut(I::Item) -> Option<B>,
{
#[inline]
fn next_back(&mut self) -> Option<B> {
#[inline]
fn find<T, B>(
f: &mut impl FnMut(T) -> Option<B>,
) -> impl FnMut((), T) -> LoopState<(), B> + '_ {
move |(), x| match f(x) {
Some(x) => LoopState::Break(x),
None => LoopState::Continue(()),
}
}
self.iter.try_rfold((), find(&mut self.f)).break_value()
}
#[inline]
fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
self.iter.try_rfold(init, filter_map_try_fold(&mut self.f, fold))
}
#[inline]
fn rfold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc
where
Fold: FnMut(Acc, Self::Item) -> Acc,
{
self.iter.rfold(init, filter_map_fold(self.f, fold))
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<B, I: FusedIterator, F> FusedIterator for FilterMap<I, F> where F: FnMut(I::Item) -> Option<B> {}
/// An iterator that yields the current count and the element during iteration.
///
/// This `struct` is created by the [`enumerate`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`enumerate`]: trait.Iterator.html#method.enumerate
/// [`Iterator`]: trait.Iterator.html
#[derive(Clone, Debug)]
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Enumerate<I> {
iter: I,
count: usize,
}
impl<I> Enumerate<I> {
pub(super) fn new(iter: I) -> Enumerate<I> {
Enumerate { iter, count: 0 }
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> Iterator for Enumerate<I>
where
I: Iterator,
{
type Item = (usize, <I as Iterator>::Item);
/// # Overflow Behavior
///
/// The method does no guarding against overflows, so enumerating more than
/// `usize::MAX` elements either produces the wrong result or panics. If
/// debug assertions are enabled, a panic is guaranteed.
///
/// # Panics
///
/// Might panic if the index of the element overflows a `usize`.
#[inline]
fn next(&mut self) -> Option<(usize, <I as Iterator>::Item)> {
let a = self.iter.next()?;
let i = self.count;
// Possible undefined overflow.
AddAssign::add_assign(&mut self.count, 1);
Some((i, a))
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
#[inline]
fn nth(&mut self, n: usize) -> Option<(usize, I::Item)> {
let a = self.iter.nth(n)?;
// Possible undefined overflow.
let i = Add::add(self.count, n);
self.count = Add::add(i, 1);
Some((i, a))
}
#[inline]
fn count(self) -> usize {
self.iter.count()
}
#[inline]
fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
#[inline]
fn enumerate<'a, T, Acc, R>(
count: &'a mut usize,
mut fold: impl FnMut(Acc, (usize, T)) -> R + 'a,
) -> impl FnMut(Acc, T) -> R + 'a {
move |acc, item| {
let acc = fold(acc, (*count, item));
// Possible undefined overflow.
AddAssign::add_assign(count, 1);
acc
}
}
self.iter.try_fold(init, enumerate(&mut self.count, fold))
}
#[inline]
fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc
where
Fold: FnMut(Acc, Self::Item) -> Acc,
{
#[inline]
fn enumerate<T, Acc>(
mut count: usize,
mut fold: impl FnMut(Acc, (usize, T)) -> Acc,
) -> impl FnMut(Acc, T) -> Acc {
move |acc, item| {
let acc = fold(acc, (count, item));
// Possible undefined overflow.
AddAssign::add_assign(&mut count, 1);
acc
}
}
self.iter.fold(init, enumerate(self.count, fold))
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> DoubleEndedIterator for Enumerate<I>
where
I: ExactSizeIterator + DoubleEndedIterator,
{
#[inline]
fn next_back(&mut self) -> Option<(usize, <I as Iterator>::Item)> {
let a = self.iter.next_back()?;
let len = self.iter.len();
// Can safely add, `ExactSizeIterator` promises that the number of
// elements fits into a `usize`.
Some((self.count + len, a))
}
#[inline]
fn nth_back(&mut self, n: usize) -> Option<(usize, <I as Iterator>::Item)> {
let a = self.iter.nth_back(n)?;
let len = self.iter.len();
// Can safely add, `ExactSizeIterator` promises that the number of
// elements fits into a `usize`.
Some((self.count + len, a))
}
#[inline]
fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
// Can safely add and subtract the count, as `ExactSizeIterator` promises
// that the number of elements fits into a `usize`.
fn enumerate<T, Acc, R>(
mut count: usize,
mut fold: impl FnMut(Acc, (usize, T)) -> R,
) -> impl FnMut(Acc, T) -> R {
move |acc, item| {
count -= 1;
fold(acc, (count, item))
}
}
let count = self.count + self.iter.len();
self.iter.try_rfold(init, enumerate(count, fold))
}
#[inline]
fn rfold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc
where
Fold: FnMut(Acc, Self::Item) -> Acc,
{
// Can safely add and subtract the count, as `ExactSizeIterator` promises
// that the number of elements fits into a `usize`.
fn enumerate<T, Acc>(
mut count: usize,
mut fold: impl FnMut(Acc, (usize, T)) -> Acc,
) -> impl FnMut(Acc, T) -> Acc {
move |acc, item| {
count -= 1;
fold(acc, (count, item))
}
}
let count = self.count + self.iter.len();
self.iter.rfold(init, enumerate(count, fold))
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> ExactSizeIterator for Enumerate<I>
where
I: ExactSizeIterator,
{
fn len(&self) -> usize {
self.iter.len()
}
fn is_empty(&self) -> bool {
self.iter.is_empty()
}
}
#[doc(hidden)]
unsafe impl<I> TrustedRandomAccess for Enumerate<I>
where
I: TrustedRandomAccess,
{
unsafe fn get_unchecked(&mut self, i: usize) -> (usize, I::Item) {
(self.count + i, self.iter.get_unchecked(i))
}
fn may_have_side_effect() -> bool {
I::may_have_side_effect()
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<I> FusedIterator for Enumerate<I> where I: FusedIterator {}
#[unstable(feature = "trusted_len", issue = "37572")]
unsafe impl<I> TrustedLen for Enumerate<I> where I: TrustedLen {}
/// An iterator with a `peek()` that returns an optional reference to the next
/// element.
///
/// This `struct` is created by the [`peekable`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`peekable`]: trait.Iterator.html#method.peekable
/// [`Iterator`]: trait.Iterator.html
#[derive(Clone, Debug)]
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Peekable<I: Iterator> {
iter: I,
/// Remember a peeked value, even if it was None.
peeked: Option<Option<I::Item>>,
}
impl<I: Iterator> Peekable<I> {
pub(super) fn new(iter: I) -> Peekable<I> {
Peekable { iter, peeked: None }
}
}
// Peekable must remember if a None has been seen in the `.peek()` method.
// It ensures that `.peek(); .peek();` or `.peek(); .next();` only advances the
// underlying iterator at most once. This does not by itself make the iterator
// fused.
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator> Iterator for Peekable<I> {
type Item = I::Item;
#[inline]
fn next(&mut self) -> Option<I::Item> {
match self.peeked.take() {
Some(v) => v,
None => self.iter.next(),
}
}
#[inline]
#[rustc_inherit_overflow_checks]
fn count(mut self) -> usize {
match self.peeked.take() {
Some(None) => 0,
Some(Some(_)) => 1 + self.iter.count(),
None => self.iter.count(),
}
}
#[inline]
fn nth(&mut self, n: usize) -> Option<I::Item> {
match self.peeked.take() {
Some(None) => None,
Some(v @ Some(_)) if n == 0 => v,
Some(Some(_)) => self.iter.nth(n - 1),
None => self.iter.nth(n),
}
}
#[inline]
fn last(mut self) -> Option<I::Item> {
let peek_opt = match self.peeked.take() {
Some(None) => return None,
Some(v) => v,
None => None,
};
self.iter.last().or(peek_opt)
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let peek_len = match self.peeked {
Some(None) => return (0, Some(0)),
Some(Some(_)) => 1,
None => 0,
};
let (lo, hi) = self.iter.size_hint();
let lo = lo.saturating_add(peek_len);
let hi = match hi {
Some(x) => x.checked_add(peek_len),
None => None,
};
(lo, hi)
}
#[inline]
fn try_fold<B, F, R>(&mut self, init: B, mut f: F) -> R
where
Self: Sized,
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,
{
let acc = match self.peeked.take() {
Some(None) => return Try::from_ok(init),
Some(Some(v)) => f(init, v)?,
None => init,
};
self.iter.try_fold(acc, f)
}
#[inline]
fn fold<Acc, Fold>(self, init: Acc, mut fold: Fold) -> Acc
where
Fold: FnMut(Acc, Self::Item) -> Acc,
{
let acc = match self.peeked {
Some(None) => return init,
Some(Some(v)) => fold(init, v),
None => init,
};
self.iter.fold(acc, fold)
}
}
#[stable(feature = "double_ended_peek_iterator", since = "1.38.0")]
impl<I> DoubleEndedIterator for Peekable<I>
where
I: DoubleEndedIterator,
{
#[inline]
fn next_back(&mut self) -> Option<Self::Item> {
self.iter.next_back().or_else(|| self.peeked.take().and_then(|x| x))
}
#[inline]
fn try_rfold<B, F, R>(&mut self, init: B, mut f: F) -> R
where
Self: Sized,
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,
{
match self.peeked.take() {
Some(None) => Try::from_ok(init),
Some(Some(v)) => match self.iter.try_rfold(init, &mut f).into_result() {
Ok(acc) => f(acc, v),
Err(e) => {
self.peeked = Some(Some(v));
Try::from_error(e)
}
},
None => self.iter.try_rfold(init, f),
}
}
#[inline]
fn rfold<Acc, Fold>(self, init: Acc, mut fold: Fold) -> Acc
where
Fold: FnMut(Acc, Self::Item) -> Acc,
{
match self.peeked {
Some(None) => init,
Some(Some(v)) => {
let acc = self.iter.rfold(init, &mut fold);
fold(acc, v)
}
None => self.iter.rfold(init, fold),
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: ExactSizeIterator> ExactSizeIterator for Peekable<I> {}
#[stable(feature = "fused", since = "1.26.0")]
impl<I: FusedIterator> FusedIterator for Peekable<I> {}
impl<I: Iterator> Peekable<I> {
/// Returns a reference to the next() value without advancing the iterator.
///
/// Like [`next`], if there is a value, it is wrapped in a `Some(T)`.
/// But if the iteration is over, `None` is returned.
///
/// [`next`]: trait.Iterator.html#tymethod.next
///
/// Because `peek()` returns a reference, and many iterators iterate over
/// references, there can be a possibly confusing situation where the
/// return value is a double reference. You can see this effect in the
/// examples below.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let xs = [1, 2, 3];
///
/// let mut iter = xs.iter().peekable();
///
/// // peek() lets us see into the future
/// assert_eq!(iter.peek(), Some(&&1));
/// assert_eq!(iter.next(), Some(&1));
///
/// assert_eq!(iter.next(), Some(&2));
///
/// // The iterator does not advance even if we `peek` multiple times
/// assert_eq!(iter.peek(), Some(&&3));
/// assert_eq!(iter.peek(), Some(&&3));
///
/// assert_eq!(iter.next(), Some(&3));
///
/// // After the iterator is finished, so is `peek()`
/// assert_eq!(iter.peek(), None);
/// assert_eq!(iter.next(), None);
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn peek(&mut self) -> Option<&I::Item> {
let iter = &mut self.iter;
self.peeked.get_or_insert_with(|| iter.next()).as_ref()
}
}
/// An iterator that rejects elements while `predicate` returns `true`.
///
/// This `struct` is created by the [`skip_while`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`skip_while`]: trait.Iterator.html#method.skip_while
/// [`Iterator`]: trait.Iterator.html
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct SkipWhile<I, P> {
iter: I,
flag: bool,
predicate: P,
}
impl<I, P> SkipWhile<I, P> {
pub(super) fn new(iter: I, predicate: P) -> SkipWhile<I, P> {
SkipWhile { iter, flag: false, predicate }
}
}
#[stable(feature = "core_impl_debug", since = "1.9.0")]
impl<I: fmt::Debug, P> fmt::Debug for SkipWhile<I, P> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("SkipWhile").field("iter", &self.iter).field("flag", &self.flag).finish()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator, P> Iterator for SkipWhile<I, P>
where
P: FnMut(&I::Item) -> bool,
{
type Item = I::Item;
#[inline]
fn next(&mut self) -> Option<I::Item> {
fn check<'a, T>(
flag: &'a mut bool,
pred: &'a mut impl FnMut(&T) -> bool,
) -> impl FnMut(&T) -> bool + 'a {
move |x| {
if *flag || !pred(x) {
*flag = true;
true
} else {
false
}
}
}
let flag = &mut self.flag;
let pred = &mut self.predicate;
self.iter.find(check(flag, pred))
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (_, upper) = self.iter.size_hint();
(0, upper) // can't know a lower bound, due to the predicate
}
#[inline]
fn try_fold<Acc, Fold, R>(&mut self, mut init: Acc, mut fold: Fold) -> R
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
if !self.flag {
match self.next() {
Some(v) => init = fold(init, v)?,
None => return Try::from_ok(init),
}
}
self.iter.try_fold(init, fold)
}
#[inline]
fn fold<Acc, Fold>(mut self, mut init: Acc, mut fold: Fold) -> Acc
where
Fold: FnMut(Acc, Self::Item) -> Acc,
{
if !self.flag {
match self.next() {
Some(v) => init = fold(init, v),
None => return init,
}
}
self.iter.fold(init, fold)
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<I, P> FusedIterator for SkipWhile<I, P>
where
I: FusedIterator,
P: FnMut(&I::Item) -> bool,
{
}
/// An iterator that only accepts elements while `predicate` returns `true`.
///
/// This `struct` is created by the [`take_while`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`take_while`]: trait.Iterator.html#method.take_while
/// [`Iterator`]: trait.Iterator.html
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct TakeWhile<I, P> {
iter: I,
flag: bool,
predicate: P,
}
impl<I, P> TakeWhile<I, P> {
pub(super) fn new(iter: I, predicate: P) -> TakeWhile<I, P> {
TakeWhile { iter, flag: false, predicate }
}
}
#[stable(feature = "core_impl_debug", since = "1.9.0")]
impl<I: fmt::Debug, P> fmt::Debug for TakeWhile<I, P> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("TakeWhile").field("iter", &self.iter).field("flag", &self.flag).finish()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I: Iterator, P> Iterator for TakeWhile<I, P>
where
P: FnMut(&I::Item) -> bool,
{
type Item = I::Item;
#[inline]
fn next(&mut self) -> Option<I::Item> {
if self.flag {
None
} else {
let x = self.iter.next()?;
if (self.predicate)(&x) {
Some(x)
} else {
self.flag = true;
None
}
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
if self.flag {
(0, Some(0))
} else {
let (_, upper) = self.iter.size_hint();
(0, upper) // can't know a lower bound, due to the predicate
}
}
#[inline]
fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
fn check<'a, T, Acc, R: Try<Ok = Acc>>(
flag: &'a mut bool,
p: &'a mut impl FnMut(&T) -> bool,
mut fold: impl FnMut(Acc, T) -> R + 'a,
) -> impl FnMut(Acc, T) -> LoopState<Acc, R> + 'a {
move |acc, x| {
if p(&x) {
LoopState::from_try(fold(acc, x))
} else {
*flag = true;
LoopState::Break(Try::from_ok(acc))
}
}
}
if self.flag {
Try::from_ok(init)
} else {
let flag = &mut self.flag;
let p = &mut self.predicate;
self.iter.try_fold(init, check(flag, p, fold)).into_try()
}
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<I, P> FusedIterator for TakeWhile<I, P>
where
I: FusedIterator,
P: FnMut(&I::Item) -> bool,
{
}
/// An iterator that skips over `n` elements of `iter`.
///
/// This `struct` is created by the [`skip`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`skip`]: trait.Iterator.html#method.skip
/// [`Iterator`]: trait.Iterator.html
#[derive(Clone, Debug)]
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Skip<I> {
iter: I,
n: usize,
}
impl<I> Skip<I> {
pub(super) fn new(iter: I, n: usize) -> Skip<I> {
Skip { iter, n }
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> Iterator for Skip<I>
where
I: Iterator,
{
type Item = <I as Iterator>::Item;
#[inline]
fn next(&mut self) -> Option<I::Item> {
if self.n == 0 {
self.iter.next()
} else {
let old_n = self.n;
self.n = 0;
self.iter.nth(old_n)
}
}
#[inline]
fn nth(&mut self, n: usize) -> Option<I::Item> {
// Can't just add n + self.n due to overflow.
if self.n == 0 {
self.iter.nth(n)
} else {
let to_skip = self.n;
self.n = 0;
// nth(n) skips n+1
if self.iter.nth(to_skip - 1).is_none() {
return None;
}
self.iter.nth(n)
}
}
#[inline]
fn count(self) -> usize {
self.iter.count().saturating_sub(self.n)
}
#[inline]
fn last(mut self) -> Option<I::Item> {
if self.n == 0 {
self.iter.last()
} else {
let next = self.next();
if next.is_some() {
// recurse. n should be 0.
self.last().or(next)
} else {
None
}
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (lower, upper) = self.iter.size_hint();
let lower = lower.saturating_sub(self.n);
let upper = match upper {
Some(x) => Some(x.saturating_sub(self.n)),
None => None,
};
(lower, upper)
}
#[inline]
fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
let n = self.n;
self.n = 0;
if n > 0 {
// nth(n) skips n+1
if self.iter.nth(n - 1).is_none() {
return Try::from_ok(init);
}
}
self.iter.try_fold(init, fold)
}
#[inline]
fn fold<Acc, Fold>(mut self, init: Acc, fold: Fold) -> Acc
where
Fold: FnMut(Acc, Self::Item) -> Acc,
{
if self.n > 0 {
// nth(n) skips n+1
if self.iter.nth(self.n - 1).is_none() {
return init;
}
}
self.iter.fold(init, fold)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> ExactSizeIterator for Skip<I> where I: ExactSizeIterator {}
#[stable(feature = "double_ended_skip_iterator", since = "1.9.0")]
impl<I> DoubleEndedIterator for Skip<I>
where
I: DoubleEndedIterator + ExactSizeIterator,
{
fn next_back(&mut self) -> Option<Self::Item> {
if self.len() > 0 { self.iter.next_back() } else { None }
}
#[inline]
fn nth_back(&mut self, n: usize) -> Option<I::Item> {
let len = self.len();
if n < len {
self.iter.nth_back(n)
} else {
if len > 0 {
// consume the original iterator
self.iter.nth_back(len - 1);
}
None
}
}
fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
fn check<T, Acc, R: Try<Ok = Acc>>(
mut n: usize,
mut fold: impl FnMut(Acc, T) -> R,
) -> impl FnMut(Acc, T) -> LoopState<Acc, R> {
move |acc, x| {
n -= 1;
let r = fold(acc, x);
if n == 0 { LoopState::Break(r) } else { LoopState::from_try(r) }
}
}
let n = self.len();
if n == 0 {
Try::from_ok(init)
} else {
self.iter.try_rfold(init, check(n, fold)).into_try()
}
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<I> FusedIterator for Skip<I> where I: FusedIterator {}
/// An iterator that only iterates over the first `n` iterations of `iter`.
///
/// This `struct` is created by the [`take`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`take`]: trait.Iterator.html#method.take
/// [`Iterator`]: trait.Iterator.html
#[derive(Clone, Debug)]
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Take<I> {
pub(super) iter: I,
pub(super) n: usize,
}
impl<I> Take<I> {
pub(super) fn new(iter: I, n: usize) -> Take<I> {
Take { iter, n }
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> Iterator for Take<I>
where
I: Iterator,
{
type Item = <I as Iterator>::Item;
#[inline]
fn next(&mut self) -> Option<<I as Iterator>::Item> {
if self.n != 0 {
self.n -= 1;
self.iter.next()
} else {
None
}
}
#[inline]
fn nth(&mut self, n: usize) -> Option<I::Item> {
if self.n > n {
self.n -= n + 1;
self.iter.nth(n)
} else {
if self.n > 0 {
self.iter.nth(self.n - 1);
self.n = 0;
}
None
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
if self.n == 0 {
return (0, Some(0));
}
let (lower, upper) = self.iter.size_hint();
let lower = cmp::min(lower, self.n);
let upper = match upper {
Some(x) if x < self.n => Some(x),
_ => Some(self.n),
};
(lower, upper)
}
#[inline]
fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
fn check<'a, T, Acc, R: Try<Ok = Acc>>(
n: &'a mut usize,
mut fold: impl FnMut(Acc, T) -> R + 'a,
) -> impl FnMut(Acc, T) -> LoopState<Acc, R> + 'a {
move |acc, x| {
*n -= 1;
let r = fold(acc, x);
if *n == 0 { LoopState::Break(r) } else { LoopState::from_try(r) }
}
}
if self.n == 0 {
Try::from_ok(init)
} else {
let n = &mut self.n;
self.iter.try_fold(init, check(n, fold)).into_try()
}
}
}
#[stable(feature = "double_ended_take_iterator", since = "1.38.0")]
impl<I> DoubleEndedIterator for Take<I>
where
I: DoubleEndedIterator + ExactSizeIterator,
{
#[inline]
fn next_back(&mut self) -> Option<Self::Item> {
if self.n == 0 {
None
} else {
let n = self.n;
self.n -= 1;
self.iter.nth_back(self.iter.len().saturating_sub(n))
}
}
#[inline]
fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
let len = self.iter.len();
if self.n > n {
let m = len.saturating_sub(self.n) + n;
self.n -= n + 1;
self.iter.nth_back(m)
} else {
if len > 0 {
self.iter.nth_back(len - 1);
}
None
}
}
#[inline]
fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
if self.n == 0 {
Try::from_ok(init)
} else {
let len = self.iter.len();
if len > self.n && self.iter.nth_back(len - self.n - 1).is_none() {
Try::from_ok(init)
} else {
self.iter.try_rfold(init, fold)
}
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> ExactSizeIterator for Take<I> where I: ExactSizeIterator {}
#[stable(feature = "fused", since = "1.26.0")]
impl<I> FusedIterator for Take<I> where I: FusedIterator {}
#[unstable(feature = "trusted_len", issue = "37572")]
unsafe impl<I: TrustedLen> TrustedLen for Take<I> {}
/// An iterator to maintain state while iterating another iterator.
///
/// This `struct` is created by the [`scan`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`scan`]: trait.Iterator.html#method.scan
/// [`Iterator`]: trait.Iterator.html
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
#[derive(Clone)]
pub struct Scan<I, St, F> {
iter: I,
f: F,
state: St,
}
impl<I, St, F> Scan<I, St, F> {
pub(super) fn new(iter: I, state: St, f: F) -> Scan<I, St, F> {
Scan { iter, state, f }
}
}
#[stable(feature = "core_impl_debug", since = "1.9.0")]
impl<I: fmt::Debug, St: fmt::Debug, F> fmt::Debug for Scan<I, St, F> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Scan").field("iter", &self.iter).field("state", &self.state).finish()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B, I, St, F> Iterator for Scan<I, St, F>
where
I: Iterator,
F: FnMut(&mut St, I::Item) -> Option<B>,
{
type Item = B;
#[inline]
fn next(&mut self) -> Option<B> {
let a = self.iter.next()?;
(self.f)(&mut self.state, a)
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let (_, upper) = self.iter.size_hint();
(0, upper) // can't know a lower bound, due to the scan function
}
#[inline]
fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
fn scan<'a, T, St, B, Acc, R: Try<Ok = Acc>>(
state: &'a mut St,
f: &'a mut impl FnMut(&mut St, T) -> Option<B>,
mut fold: impl FnMut(Acc, B) -> R + 'a,
) -> impl FnMut(Acc, T) -> LoopState<Acc, R> + 'a {
move |acc, x| match f(state, x) {
None => LoopState::Break(Try::from_ok(acc)),
Some(x) => LoopState::from_try(fold(acc, x)),
}
}
let state = &mut self.state;
let f = &mut self.f;
self.iter.try_fold(init, scan(state, f, fold)).into_try()
}
}
/// An iterator that yields `None` forever after the underlying iterator
/// yields `None` once.
///
/// This `struct` is created by the [`fuse`] method on [`Iterator`]. See its
/// documentation for more.
///
/// [`fuse`]: trait.Iterator.html#method.fuse
/// [`Iterator`]: trait.Iterator.html
#[derive(Clone, Debug)]
#[must_use = "iterators are lazy and do nothing unless consumed"]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Fuse<I> {
iter: I,
done: bool,
}
impl<I> Fuse<I> {
pub(super) fn new(iter: I) -> Fuse<I> {
Fuse { iter, done: false }
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<I> FusedIterator for Fuse<I> where I: Iterator {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> Iterator for Fuse<I>
where
I: Iterator,
{
type Item = <I as Iterator>::Item;
#[inline]
default fn next(&mut self) -> Option<<I as Iterator>::Item> {
if self.done {
None
} else {
let next = self.iter.next();
self.done = next.is_none();
next
}
}
#[inline]
default fn nth(&mut self, n: usize) -> Option<I::Item> {
if self.done {
None
} else {
let nth = self.iter.nth(n);
self.done = nth.is_none();
nth
}
}
#[inline]
default fn last(self) -> Option<I::Item> {
if self.done { None } else { self.iter.last() }
}
#[inline]
default fn count(self) -> usize {
if self.done { 0 } else { self.iter.count() }
}
#[inline]
default fn size_hint(&self) -> (usize, Option<usize>) {
if self.done { (0, Some(0)) } else { self.iter.size_hint() }
}
#[inline]
default fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
if self.done {
Try::from_ok(init)
} else {
let acc = self.iter.try_fold(init, fold)?;
self.done = true;
Try::from_ok(acc)
}
}
#[inline]
default fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc
where
Fold: FnMut(Acc, Self::Item) -> Acc,
{
if self.done { init } else { self.iter.fold(init, fold) }
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<I> DoubleEndedIterator for Fuse<I>
where
I: DoubleEndedIterator,
{
#[inline]
default fn next_back(&mut self) -> Option<<I as Iterator>::Item> {
if self.done {
None
} else {
let next = self.iter.next_back();
self.done = next.is_none();
next
}
}
#[inline]
default fn nth_back(&mut self, n: usize) -> Option<<I as Iterator>::Item> {
if self.done {
None
} else {
let nth = self.iter.nth_back(n);
self.done = nth.is_none();
nth
}
}
#[inline]
default fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
if self.done {
Try::from_ok(init)
} else {
let acc = self.iter.try_rfold(init, fold)?;
self.done = true;
Try::from_ok(acc)
}
}
#[inline]
default fn rfold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc
where
Fold: FnMut(Acc, Self::Item) -> Acc,
{
if self.done { init } else { self.iter.rfold(init, fold) }
}
}
unsafe impl<I> TrustedRandomAccess for Fuse<I>
where
I: TrustedRandomAccess,
{
unsafe fn get_unchecked(&mut self, i: usize) -> I::Item {
self.iter.get_unchecked(i)
}
fn may_have_side_effect() -> bool {
I::may_have_side_effect()
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<I> Iterator for Fuse<I>
where
I: FusedIterator,
{
#[inline]
fn next(&mut self) -> Option<<I as Iterator>::Item> {
self.iter.next()
}
#[inline]
fn nth(&mut self, n: usize) -> Option<I::Item> {
self.iter.nth(n)
}
#[inline]
fn last(self) -> Option<I::Item> {
self.iter.last()
}
#[inline]
fn count(self) -> usize {
self.iter.count()
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
#[inline]
fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R
where
Self: Sized,
Fold: FnMut(Acc, Self::Item) -> R,
R: Try<Ok = Acc>,
{
self.iter.try_fold(init, fold)
}
#[inline]
fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc
where
Fold: FnMut(Acc, Self::Item) -> Acc,
{
self.iter.fold(init, fold)
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<I> DoubleEndedIterator for Fuse<I>
where
I: DoubleEndedIterator + FusedIterator,
{
#[inline]
fn next_back(&mut self) -> Option<<I as Iterator>::Item> {
self.iter.next_back()